How accurate is the BOD POD?
Research studies at major universities established the outstanding accuracy, safety, and speed of the BOD POD. Before the BOD POD, the most accepted method was underwater weighing (the “dunk tank”). When comparing the two methods, the BOD POD and underwater weighing often produce identical results. Many top scientists consider the BOD POD to be even more accurate than underwater weighing because testing with the BOD POD is so reproducible from test to test. The general error range of the BOD POD is 1-2% (the same as hydrostatic weighing).
Why is this accurate?
Densitometry is the clinical standard for fat and fat-free measurements. There are three types of densitometry measurements, the first and oldest method is Hydrostatic Weighing, the second is semi-submerged plethysmography, where the tester is submerged up to their neck in water, and then has their head tested with air displacement, finally full air displacement plethysmography. All three methods end up with whole body density measurement. Hydrostatic requires you to blow out all your air, then go underwater and blow out more while holding still, which is very unnatural for most people. The BOD POD requires breathing normally while sitting still which makes it a more repeatable and comfortable test. In clinical settings, the three methods typically have very similar accuracies.
How does the BOD POD measure body composition?
BOD POD system measures body composition by determining body volume and body weight. Once those two variables are determined, body density can be computed and inserted into an equation to provide percent fat measurements. Body weight is easily determined by the use of an accurate scale. Body volume is determined by applying the gas law (p1V1=p2V2), an expansion of Boyle´s Law, pV=c. The BOD POD measures volume by monitoring changes in pressure within a closed chamber. These pressure changes are achieved by oscillating a speaker mounted between the front testing chamber and a rear reference chamber, which causes complementary pressure changes in each chamber. The pressure changes are very small and are not noticed by the individual being tested.
Three measurements are performed to determine body volume. The volume of the subject chamber while empty is the first measurement taken by the BOD POD. The second measurement is the volume of the subject chamber with the subject inside. By subtraction, the volume of the subject is determined. Combined with the measurement of mass, the subject’s density is determined and subsequently their body composition is determined
Understanding The Numbers
Knowing your body fat percentage is an important first step at the onset of any fitness or dietary program. An accurate body composition analysis provides a baseline for tracking progress, in addition to offering motivational feedback along the way. Be sure to measure your body composition regularly as you work towards your fitness and nutritional goals.